Method for producing twin pistons



July 28, 1959 H. SCHMIDT ETIAL 2,896,316

METHOD FOR PRODUCING TWIN PISTONS Filed Aug. 17, 1955 2 Sheets-Sheet 1 3 Fig.3

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United States Patent METHOD FOR PRODUCING TWIN PISTONS Hans Schmidt and Giinter Dunkel, Kassel, Germany, assignors to LicentiaPatent-Verwaltungs-G.m.b.H., Hamburg, Germany 'Application August 17, 1955, Serial No. 528,881 Claims priority, application Germany February 4, 1955 6 Claims. (Cl. 29-411) The present invention relates to the manufacture of twin pistons of the type used for refrigerator compressors, and more particularly to a method of aligning surface portions of resiliently connected twin pistons.

' Twin pistons frequently cause considerable production difiiculties due to misalignment which may lead to excessive wear of the pistons and cylinders.

Another difficulty arises due to the fact that each piston must be independently finished whereby the unavoidable finislr'ingtolerances have an unfavorable effect. Due to the resilient connection between the two pistons the two pistons cannot be simultaneously finished.

It is most advantageous to connect the twin pistons to a resilient connecting rod by brazing, but such brazing requires a temperature which necessitates a finishing of the piston surface after brazing, and as pointed out above the surface portions of the pistons cannot be accurately aligned while the same are resiliently connected.

It is one object of the present invention to overcome the disadvantages of resiliently connected twin pistons and to provide a method for producing resiliently connected twin pistons having exactly aligned surface por tions.

It is another object of the present invention to connect a pair of bodies by a resilient connecting member brazed to the two bodies and to finish the aligned surface portions of the two bodies after making a temporary rigid connection between the two bodies.

It is a further object of the present invention to finish surface portions of a pair of twin pistons when the same are rigidly and resiliently connected and then to remove the rigid connection so that only the resilient connection is maintained.

It is another object of the present invention to produce the resilient connection by brazing in a protective atmosphere, preferably using copper.

With these objects in view the present invention mainly consists in a method of producing resiliently connected bodies having aligned surface portions and comprising the steps of resiliently connecting at least two rigidly connected bodies, finishing surface portions of the rigidly and resiliently connected bodies to align these surface portions, and interrupting the rigid connection between the two bodies while maintaining the resilient connection between the same.

According to a preferred method of the present invention a rigid connection and a resilient connection is made between the two bodies whereupon surface portions of the rigidly and resiliently connected bodies are finished and aligned; After the surface portions are finished, the rigid connection between the two bodies is interrupted, for instance by cutting through the rigid connection, or by removing a rigid clamping member holding the bodies together.

The method of the present invention is particularly advantageously applied to twin pistons such as used for This type of twin pistons is rigidly connected to opposite sides of a crank slide. Ac-

2,896,316 Patented July 28, 1959 cording to a preferred method of the present inventionthe twin pistons are brazed to the crank slide while in the same operation one of the twin pistons is connected to the crank slide by a resilient rod. Thereupon, the wall of the resiliently connected piston is cut through so that one of the pistons is resiliently connected to the crank slide and the other of the pistons is rigidly connected to the crank slide. The brazing is preferably carried out in a brazing furnace using copper in a protective atmosphere.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Figs. 1 and 2 are axial sectional views of a pair of twin pistons during two consecutive steps of the present invention;

Fig. 3 is an axial sectional view of an arrangement for carrying out a modified method of the present invention;

Fig. 4 is a fragmentary sectional view illustrating a detail of Fig. 3;

Fig. 5 is an axial sectional View of an arrangement for carrying out another method according to the'present invention;

Fig. 6 is a plan view of the arrangement shown in Fig. 5, partly in section, the section being taken along line VIVI in Fig. 5;

Fig. 7 is an axial sectional view of another arrangement according to the present invention; and

Fig. 8 is a cross sectional view of the arrangement shown in Fig. 7, the section being taken along line- VIII--VIII in Fig. 7.

Referring now to the drawings, and more particularly to Figs. 1 and 2, a pair of twin pistons 1 and 2 are rigidly attached, preferably by brazing, to the crank slide 3. An attaching member 6 is brazed to the crank slide ,3, end plates 5, 5 are brazed to the outer ends of the hollow pistons 2 and 1, respectively. A resilient connecting rod 4 is brazed at the ends thereof to the members 5 and 6, respectively. In this condition the outer cylindrical surfaces of the pistons 1 and 2 are finished, for instance by grinding, so that the cylindrical surface portions of the two pistons 1 and 2 are exactly aligned. Thereupon, the piston 2 is cut through as shown in Fig. 2 so that the rigid connection between piston 2 and the crankslide 3 is interrupted and only the resilient connection by means of the rod 4 remains. Consequently, when the pistons 1 and 2 are reciprocated in corresponding cylinders, slight inaccuracies caused by tolerances are compensated by the resilient giving of the rod 4.

It will be understood that a crank pin is located in the slot of the crank slide 3 so that during rotation of the crank the crank pin moves up and down in the slot of the crank slide 3 while the twin pistons 1 and 2 are reciprocated in axial direction.

In the embodiment illustrated in Figs. 3 and 4, the piston 1 having an end plate 5 is rigidly attached to the crank slide 3, and a tubular member 7 is rigidly attached to the opposite side of the crank slide 3. The other twin piston 2 is resiliently connected to the crank slide 3 by means of a resilient rod 4 attached both to member 6 and its end plate 5, the members 2, 5, '4, and members 6 and 3, respectively, being connected by brazing. The rod 4 holds the piston 2 in a substantially coaxial position with the piston 1, but before the outer cylindrical surface portions of the pistons 1 and 2 are finished, the piston 2 is clamped to the tubular member 7 by a clamping member. In the illustrated arrangement the clamp pistons.

member 8 is a ring including at least two separable ring portions and having a T-shaped cross section. The ring portions are placed between the tubular member 7 and the piston 2, and thereupon clamped to these members by a tension wire 9. Thereby a rigid connection is obtained between the piston 2 and the crank slide 3, and the other piston '1, respectively. The surfaces of the pistons 1 and 2 are now finished while the pistons are rigidly connected so that a perfect surface portion can be obtained. After that the wire 9 is broken, and the clamping ring 8 removed so that only a resilient connection by means of the rod 4% remains.

In order to facilitate the finishing operations of the piston surface, the portions of the tubular member 7 and of the piston 2 against which the flange of the clamping ring 8 abuts, are reduced in diameter as best seen in Fig. 4.

It is also possible to omit the wire loop 9, and to temporarily solder the ring 8 to members 2 and 7 after the brazing operations have been completed. The soldered ring 8 rigidly connects the piston 2 to the tubular member 7 and to the crank slide 3 during the finishing operations, whereupon the soldered connection is dissolved and the ring 8 removed.

Figs. and 6 show a modified embodiment of the present invention. According to this embodiment the twin pistons 1 and 2 are provided with end plates 5 and 5 brazed to the outer ends of the same. A resilient connection is formed between the pistons 1 and 2 by a resilient rod 4. The resilient rod 4 projects into bores in the end plates 5 and 5 and is brazed to the end plates. A rigid bridging member such as a flat bar 711 is simultaneously brazed to the pistons 1 and 2 and forms a rigid connection between the same. In this arrangement the crank slide 3 is transversely spaced from the twin pistons, and the twin pistons are attached to the crank slide 3 by screws passing through the rigid connecting member 7a and into crank slide 3. In this embodiment as well as in the above-described embodiments all brazing steps are carried out simultaneously in a brazing furnace, and thereupon the rigidly connected twin pistons are fimshed to align the working surfaces thereof, which may have been deformed due to the influence of the high temperature in the brazing furnace. After the surfaces are aligned, the connection 7a is cut through as clearly shown at 7b in Figs. 5 and 6 so that only the piston 1S rigidly attached to the crank slide 3, whereas the piston 1 is resiliently connected to the piston 2, and thereby to the crank slide 3. The unit 1, 2, 4, 7a is attached to the crank slide 3 after the pistons 1 and 2 have been fitted into the corresponding cylinders.

Figs. 7 and 8 illustrate an arrangement in which a cylindrical tubular member 10 is used for producing the twin The tubular member 10 is closed at the ends thereof by end plates 5 and 5' which are brazed thereto, and a resilient rod 4 is brazed to the end members 5 and 6. Preferably, an annular member ill surrounding the rod 4 is brazed into the 'nterior of the tubular member 10. Axially spaced surface portions of the cylindrical tubular member 10 are finished to align the same, whereupon the tubular member 10 is cut at the point 10 located intermediate the finishing surface portions. Consequently, the finished surface portions are no longer rigidly connected and a pair of twin pistons is formed which are resiliently connected by the rod 4.

As best seen in Fig. 8 the tubular member 10 is formed with a pair of slots 10a permitting the insertion of screws 12 by which the annular member 11, and thereby the twin piston unit is attached to an abutment 7b which is rigidly secured to the crank slide 3.

It will be understood that the arrangement of the present invention is not only applicable to twin pistons but may be advantageously used for other resiliently connected bodies requiring aligned surface portions such as short thick shafts which are exposed to sudden transverse loads.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of methods for producing aligned surface portions on resiliently connected bodies differing from. the types described above.

While the invention has been illustrated and described as embodied in a method for producing aligned surface portions on resiliently connected twin pistons, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A method of producing aligned surface portions on resiliently connected coaxial twin pistons comprising the steps of brazing a rigid connecting member to a pair of independent hollow substantially coaxial pot-shaped pistons, and simultaneously brazing a resilient rod located in the axis of said pistons to the outwardly located end plates of said pot-shaped pistons whereby said pistons are resiliently and rigidly connected; finishing surface portions of said pistons to align said surface portions of the same; and cutting tln'ough said rigid connecting member whereby a pair of coaxial resiliently connected twin pistons having aligned surface portions is obtained.

2. A method of producing aligned surface portions on resiliently connected coaxial twin pistons comprising the steps of brazing end plates to the ends of a tubular cylindrical body and brazing a resilient rod located in the axis of said tubular cylindrical body to said end plates; brazing an annular member into the inteiior of said cylindrical tubular member; finishing axially spaced surface portions of said tubular cylindrical body to align said surface portions; cutting through the wall of said tubular cylindrical body between said finished surface portions; and

attaching said annular member and thereby said pair of twin pistons to a crank slide after finishing said surface portions whereby a pair of coaxially resiliently connected twin pistons having aligned surface portions is obtained.

3. The method of producing mutually aligned coaxial surface portions on coaxial twin piston members forming part of an assembly which includes a common support member and a resilient element connecting at least two of said members, comprising the steps af both establishing a resilient connection between said two of said members by attaching one end of a resilient rod in substantially coaxial position to one of said piston members and the other end of said rod to another one of said two of said members, and of rigidly connecting both of said piston members at circumferential edge points in substantially coaxial position with said common support member at 0pposite sides thereof; thereafter finishing surface portions of each of said piston members while connected rigidly and simultaneously resiliently by said resilient element, so as to align coaxially said surface portions; and then eliminating the rigid connection of said one of said piston members and said common support member while maintaining the resilient connection between said one piston member and said other one of said two other members, whereby in the finished assembly said finished surface portions are resiliently movable in transverse direction between a co-axially aligned position and a plurality of'nonaligned positions.

4. The method of producing mutually aligned co-axial surface portions on coaxial twin piston members formmg part of an assembly which includes a common support member and a resilient element connecting at least two of said members, comprising the steps of both establishing a resilient connection between said twin piston members by attaching one end of a resilient rod in substantially coaxial position ,to one of said piston members and the other end of said rod to said common support member, and of rigidly connecting both of said piston members at circumferential edge points in substantially coaxial position with said common support member at opposite sides thereof; thereafter finishing surface portions of each of said piston members while connected rigidly and simultaneously resiliently by said resilient element, so as to align coaxially said surface portions; and then cutting through the rigid connection of said one of said piston members and said common support member while maintaining the resilient connection between said one piston member and said support members, whereby in the finished assembly said finished surface portions are resiliently movable in transverse direction between a coaxially aligned position and a plurality of non-aligned positions.

5. The method of producing mutually aligned coaxial surface portions on coaxial twin piston members forming part of an assembly which includes a common crank slide member and a resilient element connecting at least one of said piston members with said crank slide member, comprising the steps of both establishing a resilient connection between said one of said piston members with said crank slide by attaching one end of a resilient rod in substantially coaxial position to said one of said piston members and the otherend of said rod to said crank slide, and of rigidly connecting both of said piston members 6 at circumferential edge points in substantially coaxial position with said crank slide at opposite sides thereof, said one of said piston members being connected by clamping action of a clamping means applied thereto to prevent any transverse movement relative to said crank slide; thereafter finishing surface portions of each of said piston members while connected rigidly and simultaneously resiliently by said resilient element, so as to align coaxially said surface portions; and then removing said clamping means for eliminating the rigid connection of said one of said piston members with said crank slide while maintaining the resilient connection between said one piston member and said crank slide, whereby in the finished assembly said finished surface portions are resiliently movable in transverse direction between a coaxially aligned position and a plurality of non-aligned positions.

6. The method as set forth in claim 5, wherein said clamping means is a clamping ring including at least two separable ring portions having a T-shaped cross-section; and including the step of embracing said two ring portions by tension wire for clamping the same against said one of said piston members and against a cylindrical portion of said crank slide.

References Cited in the file of this patent UNITED STATES PATENTS 1,220,596 Bovard Mar. 27, 1917 1,939,772 Greene Dec. 19, 1933 2,059,822 Steenstrup Nov. 3, 1936 2,105,618 Silva Jan. 18, 1938 2,149,902 Saurer Mar. 7, 1939 2,210,993 Weatherhead Aug. 13, 1940 2,382,245 McCormack Aug. 14, 1945 2,529,348 Mustee Nov. 7, 1950 UNITED STATE S PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,896,316 July 28 1959 Hans Schmidt et al. I

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent. should read as corrected below.

In the heading to the printed specification, line 7, date of priority, for "February 4, 1955" read November 8, 1954 n Signed and sealed this 5th day of December 1961.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer I Commissioner of Patents USCOMM-DC- 

